Gordon L. Brownell; invention evolved into the PET scan; at 86

A 7-year-old daughter of a Rhode Island farmer traveled to Boston in 1953 when doctors couldn't diagnose a neurological malady that left her unable to read and looking around with a vacant stare. Even her neurosurgeon at Massachusetts General Hospital was perplexed, so he enlisted the help of a colleague Dr. Gordon L. Brownell, who proceeded to write a chapter in the history of nuclear medicine.

As Time magazine reported the following year, Dr. Brownell developed a scanning machine that isolated, within a third of an inch, the location of a tumor that the neurosurgeon successfully removed from the girl's brain.

The technology Dr. Brownell invented evolved into positron emission tomography, commonly known as a PET scan, which uses radioactive tracers to pinpoint the location of diseased tissue. He died Nov. 11 in his Salem home. Dr. Brownell was 86 and had been suffering from pneumonia and complications from throat cancer.

During a career that spanned 58 years, Dr. Brownell held a joint appointment at MGH, where since retiring he was honorary physicist in the department of radiology, and at the Massachusetts Institute of Technology, where he was professor emeritus of nuclear science and engineering.

The scientific dexterity required for those two roles may have contributed to the breakthrough 55 years ago, said Dr. Bruce R. Rosen, a former student of Dr. Brownell's who is director of the Athinoula A. Martinos Center for Biomedical Imaging at Mass General.

"He was a professor of nuclear engineering, as well as connected here in the hospital, so he understood the nuclear technology on one hand and the medical needs on the other," Rosen said. "He had this flash of brilliance to put those pieces together. For all the wonderful things he did in building upon that insight, first and foremost he had the insight, and it defined a field."

More than 50 years after Dr. Brownell invented positron emission imaging, the technology he pioneered is used "routinely in the care of patients, primarily in the care of patients with cancer," said Dr. James H. Thrall, radiologist in chief at MGH.

"What is truly remarkable is to realize there are only about five or six medical-imaging methods in use today. So to be an inventor of one of those is a major contribution."

Two years ago, a committee of the Society of Nuclear Medicine presented Dr. Brownell with the Loevinger-Berman Award for lifetime contributions.

After inventing the first positron-imaging machine in the early 1950s, he kept working to improve the technology as it flowered into positron emission tomography.

"He was an innovator and inventor who was always looking for new things," said his wife, Anna-Liisa Brownell, an associate professor in the radiology department at MGH.

While PET scans often help determine how far certain cancers have spread and how they might respond to treatment, physicians also employ the technology for purposes such as diagnosing neurological disorders and detecting decreased blood flow in the heart.

"It's really the early warning system for cancer care, because it's the most sensitive tool we have to see the smallest area of tumor growth anywhere in the body," Rosen said. "It has become an invaluable part of the way we monitor and treat cancer patients."

Over the past 55 years, Thrall and Rosen said, Dr. Brownell's technology has been used on tens of thousands of patients, saving lives in many instances.

Born in Duncan, Okla., Dr. Brownell moved with his family to Wolcott, N.Y. When he was 16, the family moved to Lewisburg, Pa., where his older brother entered Bucknell University and Dr. Brownell followed a couple of years later.

Dr. Brownell studied engineering and physics and graduated in 1943 with a bachelor of science degree. At college, he met Catherine Wittenberg, and they married in 1944.

Offered several teaching fellowships, Dr. Brownell decided to pursue his doctorate at MIT, but interrupted his studies after a semester to join the Navy. Toward the end of World War II, he worked with a naval research team to develop acoustic devices that protected US ships by detecting the presence of underwater mines.

Living on campus with his family, he completed his doctorate in physics in 1950, then established the Physics Research Laboratory at MGH while also teaching at MIT. The family later moved to Brighton and then Weston.

Not long after graduating from MIT, Dr. Brownell went to Mendoza, in western Argentina, where he and other researchers developed treatments for thyroid ailments among a population with iodine deficiencies. That research and his subsequent work developing positron imaging technology turned Dr. Brownell into a sought-after speaker who gave presentations in many countries.

"My dad was always a consummate professional," said his son David of Medway. "We didn't have too many dinner-time conversations about PTA meetings and things like that. He wasn't that kind of guy. Our conversations were about world events. He had traveled around the world before it was common to do so."

Dr. Brownell's first marriage ended in divorce. He married Anna-Liisa Pranni 22 years ago, and they lived for many years in Salem.

In his 70s, he retired from MIT and MGH, but continued the research that defined his career and launched a field of medical imaging.

In 2002, he was elected to the Institute of Medicine, a nonprofit component of the National Academy of Science whose members offer advice to policy makers in government and industry.

"A lot of people will develop something when they're young, and they'll just sit on it and do administrative work after that," his son said. "That's not my dad. He was always pushing the envelope, always trying to make the machines substantially better."

Dr. Brownell, said Thrall, "remained one of the giants in the field for more than 50 years and was active in his research up until very shortly before his death. I have to say, one of the things I believe is characteristic of the true giants of science is the fact that they never stop their inquiry."

In addition to his wife and son, Dr. Brownell leaves a daughter, Wendy Silverman of Needham; two other sons, Peter of Marlborough and James of Waltham; a stepdaughter, Piia DiMeco of Wilmington; a stepson, Janne Kairento of Beverly; a brother, Roscoe Jr. of Altoona, Pa.; five grandsons; and two granddaughters.